Flu: How viral infection causes intestinal disease

Why do we often suffer from vomiting and diarrhoea during an influenza? Influenza is an infectious respiratory disease, whereas vomiting and diarrhoea are symptoms of a gastrointestinal disease. Researches have now found the mechanism by which they are connected.

Using a mouse model of respiratory influenza infection, they found that lymphocytes (immune cells of the adaptive immune system) migrate specifically from the respiratory mucosa into the intestinal mucosa. In the intestine, these lymphocytes secrete pro-inflammatory mediators that alter the composition of the intestinal microbiota. Eventually, the loss of intestinal homeostasis leads to inflammation to cause intestinal injury and result in gastrointestinal disease symptoms.

The findings support the concept of a ‘common mucosal immune system’
The findings support the concept of a ‘common mucosal immune system’

But why do lymphocytes migrate from the lungs to the gut during an influenza infection at all? This process could represent a regulatory mechanism of the body to deal with an overwhelming immune response. It is a trade-off: Diverting the immune response from the lung into the intestine is possibly less dangerous than allowing the lung tissue to be damaged by the strong immune response.

These findings support the concept of a ‘common mucosal immune system’; an idea which assumes that immune cells and structures contained in mucosal tissues are universally connected within the body and should therefore be considered as one large but distributed ‘organ’.

doi/10.1084/jem.20140625

Written by Verena Brucklacher-Waldert.

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